Harvard Researchers Invent Stretchable Transparent Speaker

Posted on August 30, 2013

Harvard researchers have invented a transparent speaker that consists of a thin sheet of rubber sandwiched between layers of saltwater gel. Harvard reports that a high-voltage signal runs across the surfaces and through the layers forcing the rubber to rapidly contract and vibrate. This produces sounds that span the entire audible spectrum, ranging from 20 hertz to 20 kilohertz. Jeong-Yun Sun (left) and Christoph Keplinger (right) show off the ionically conductive stetchy and transparent material in the above photograph.

Jeong-Yun Sun, co-lead author and a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS), said in a statement, "It must seem counterintuitive to many people, that ionic conductors could be used in a system that requires very fast actuation, like our speaker. Yet by exploiting the rubber layer as an insulator, we're able to control the voltage at the interfaces where the gel connects to the electrodes, so we don't have to worry about unwanted chemical reactions. The input signal is an alternating current, and we use the rubber sheet as a capacitor, which blocks the flow of charge carriers through the circuit. As a result, we don't have to continuously move the ions in one direction, which would be slow; we simply redistribute them, which we can do thousands of times per second"

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